Thread cutting tools conventionally include a cutting insert secured in a fixed position to a tool holder. In prior art tools, cutting forces acting against the insert clamp, tended to cause the insert to chatter and shift its position in the holder. This adversely affected the proper performance of a cutting operation. Maintaining the position of the insert is especially important when used on numerically controlled machines where various tools are automatically positioned for different machining operations. If the insert is not securely held in the holder, the cutter position will not be repeated accurately on successive workpieces with a resulting variation in the machined products.
The present invention eliminates many of the foregoing problems by providing an insert and a cooperating holder configured in such a manner that cutting forces on the insert act to maintain the position of the insert in the tool holder. Thus, the insert is not solely dependent upon the securing clamp to maintain it in the desired position relative to the holder.
In prior art, the cutting point of thread cutting inserts normally comprise two cutting faces forming a 60 degree angle. To resharpen inserts of this type, it is necessary to grind both faces to keep the apex of the cutting surfaces in a plane bisecting the angle formed by them. The present invention utilizes a mounting face and a second face forming a 60 degree angle with it to provide a cutting tip. To resharpen only the second face is ground and the apex remains in the plane of the mounting surface.